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C. Chemistry: Chemical Reactions · Chemical Reactions

Chemical Reactions: Unit Review

A1.1 A1.2 A1.3 A1.4 A1.5 A1.6 A1.7 A1.8 A1.9 A1.10 A1.11 A1.12 A1.13 A2.1 A2.2 C1.1 C1.2 C2.1 C2.2 C2.3 C2.4 C2.5 C2.6 C3.1 C3.2 C3.3 C3.4 C3.5 C3.6 C3.7 C3.8About 40 minutes
Learning goals
  • I can name and write formulas for ionic compounds, molecular compounds and acids.
  • I can write and balance chemical equations and explain them with the law of conservation of mass.
  • I can classify reactions, predict their products, and describe acids, bases, pH and neutralization.
  • I can analyse safety and environmental issues linked to chemical reactions and how chemistry helps solve them.

Words to know

chemical reaction
A change that forms new substances with new properties.
balanced equation
An equation with the same number of each kind of atom on both sides.
law of conservation of mass
The total mass of reactants equals the total mass of products.
activity series
A ranking of metals from most to least reactive.
precipitate
A solid that forms when two solutions are mixed.
pH scale
A scale from about 0 to 14 that shows how acidic or basic a solution is.
neutralization
An acid reacts with a base to form a salt and often water.

Let's review!

In this unit you learned the language of chemical reactions: how to name and write formulas for ionic compounds (including multivalent metals and polyatomic ions), molecular compounds and acids. You looked for evidence of chemical change, wrote word equations and balanced chemical equations, built molecular models, and tested the law of conservation of mass. You sorted reactions into synthesis, decomposition, single displacement, double displacement and combustion, used the activity series and a solubility guide to predict products, and studied acids, bases, pH and neutralization. Finally, you analysed the safety and environmental issues of reactions and how chemistry helps solve environmental challenges, along with the careers and Canadian scientists involved.

This review has a few questions from every lesson. Try each one, then press Show answer to check.

SynthesisA + B → AB2Mg + O₂ → 2MgODecompositionAB → A + B2H₂O₂ → 2H₂O + O₂Single displacementA + BC → AC + BFe + CuSO₄ → FeSO₄ + CuDouble displacementAB + CD → AD + CBAgNO₃ + NaCl → AgCl + NaNO₃Combustionfuel + O₂ → CO₂ + H₂OCH₄ + 2O₂ → CO₂ + 2H₂ONeutralizationacid + base → salt + waterHCl + NaOH → NaCl + H₂O
The six kinds of reaction in this unit, with their patterns and an example of each. Neutralization is a special kind of double displacement.
1. Wordsiron + oxygen →iron(III) oxide2. FormulasFe + O₂ →Fe₂O₃3. Balance4Fe + 3O₂ →2Fe₂O₃4. CheckFe: 4 = 4O: 6 = 6 ✔
The four steps for writing any chemical equation: words, correct formulas, balance with coefficients only, then check every element.

Names, Formulas and Composition of Compounds

1

Name: (a) N₂O₃, (b) CaBr₂, (c) CuCl.

2

Write the formula for iron(III) sulfide.

3

Describe the composition of one molecule of SF₆.

Compounds with Polyatomic Ions

1

Write the formula for ammonium phosphate.

2

Name Fe(NO₃)₂.

3

How many atoms of oxygen are in Ca(ClO₃)₂?

Naming Acids and Classifying Compounds

1

Name HNO₂(aq) and H₂SO₄(aq).

2

Write the formula for hydrobromic acid.

3

Classify: (a) K₂SO₄, (b) CCl₄, (c) HCl(aq).

Evidence of Chemical Change

1

List five kinds of evidence of chemical change.

2

A reaction makes its beaker feel warm. Exothermic or endothermic?

3

Why is boiling water not a chemical change, even though bubbles form?

Word Equations, Chemical Equations and Molecular Models

1

Write the skeleton equation with state symbols: "Solid sodium reacts with chlorine gas to form solid sodium chloride."

2

In 4NH₃, how many H atoms are there?

3

What do the balls and sticks represent in a molecular model of a reaction?

The Law of Conservation of Mass

1

3.6 g of magnesium burns to form 6.0 g of magnesium oxide. What mass of oxygen reacted?

2

An open beaker of reacting chemicals loses mass. Give the most likely reason.

3

Explain, using atoms, why equations must be balanced.

Balancing Chemical Equations

1

Balance: Al + Cl₂ → AlCl₃

2

Balance: C₄H₁₀ + O₂ → CO₂ + H₂O

3

Balance: Ca(OH)₂ + H₃PO₄ → Ca₃(PO₄)₂ + H₂O

Synthesis and Decomposition Reactions

1

Classify and balance: K + O₂ → K₂O

2

Predict the products and balance the decomposition of water by electricity.

3

What test identifies hydrogen gas?

Single Displacement Reactions and the Activity Series

1

Will magnesium react with copper(II) chloride? If so, write the balanced equation.

2

Will silver react with hydrochloric acid? Explain.

3

Complete and balance: Cl₂ + NaI →

Double Displacement and Combustion Reactions

1

Predict and balance: Pb(NO₃)₂(aq) + 2NaCl(aq) →

2

Balance the complete combustion of methane.

3

Name a dangerous product of incomplete combustion and one way to protect against it.

Acids, Bases and the pH Scale

1

How many times more acidic is pH 2 than pH 4?

2

A solution turns bromothymol blue yellow. Is it acidic, neutral or basic?

3

What ion do bases produce in water?

Acid-Base Neutralization

1

Complete and balance: H₂SO₄ + Ca(OH)₂ →

2

Which acid and base make sodium nitrate?

3

Write the key ionic step in neutralization.

Chemical Reactions: Safety and Environmental Issues

1

Why does road salt make steel corrode faster?

2

Why must cyanide solutions never be mixed with acids?

3

What causes the strong smell at some indoor pools?

Using Chemistry to Solve Environmental Challenges

1

Write the equation for limestone removing SO₂ in a scrubber.

2

What did David Schindler's Lake 226 experiment show?

3

Name one career that uses chemical reactions to protect the environment and the education it needs.

Just for fun

A chemistry student was asked to sum up the whole unit in one sentence. She wrote: "Atoms never disappear; they just keep changing partners." Her teacher gave her full marks and asked whether she was writing about chemistry or about a Grade 10 dance.

How to use this review

Do two or three sections at a time rather than all at once. Write your answer before you check it. For every mistake, write down why it happened: a formula error, a balancing slip, a wrong reaction type, or an idea you did not know. Then go back to that lesson's worked examples (the parent notes below say which lesson). Keep a periodic table, a list of polyatomic ions, the activity series and the solubility guide handy, just as you would on a test. Finish with the 10-question quiz.

Check your understanding

Quiz

1.

What is the correct name for Fe₂O₃?

2.

Which is the formula for calcium nitrate?

3.

What is the name of H₂CO₃(aq)?

4.

Which equation is balanced?

5.

20.0 g of reactants react completely in a closed container. What is the mass of the products?

6.

Zn + CuSO₄ → ZnSO₄ + Cu is an example of...

7.

Which pair of solutions forms a precipitate when mixed?

8.

What are the products of the complete combustion of propane?

9.

A solution has a pH of 12. It is...

10.

Which equation shows neutralization?

For parents and teachers

How to use the review results:

  • Naming or formula errors with binary compounds or Roman numerals → revisit Names, Formulas and Composition of Compounds.
  • Missing brackets, wrong polyatomic ion formulas or atom counts → revisit Compounds with Polyatomic Ions.
  • Acid names (hydro-, -ic, -ous) or classifying ionic/molecular/acid → revisit Naming Acids and Classifying Compounds.
  • Calling physical changes chemical, or mixing up exothermic and endothermic → revisit Evidence of Chemical Change.
  • Forgetting diatomic elements, state symbols, or confusing coefficients and subscripts → revisit Word Equations, Chemical Equations and Molecular Models.
  • Missing-mass calculations or open/closed system explanations → revisit The Law of Conservation of Mass.
  • Balancing errors, especially changing subscripts or odd oxygen counts → revisit Balancing Chemical Equations.
  • Predicting products of synthesis or decomposition, or gas tests → revisit Synthesis and Decomposition Reactions.
  • Predicting whether a displacement happens → revisit Single Displacement Reactions and the Activity Series.
  • Precipitate predictions or combustion equations → revisit Double Displacement and Combustion Reactions.
  • pH direction or the factor of 10, or choosing indicators → revisit Acids, Bases and the pH Scale.
  • Building the salt or balancing neutralization equations → revisit Acid-Base Neutralization.
  • Explaining the chemistry behind corrosion, cyanide mining or pools, or judging sources → revisit Chemical Reactions: Safety and Environmental Issues.
  • Scrubbers, the Great Lakes, careers or Canadian scientists → revisit Using Chemistry to Solve Environmental Challenges.

Tip: on tests, students are usually given a periodic table and a list of polyatomic ions. Practise with those references beside you, so the review feels like the real thing.